There are known residual-current circuit breakers that are designed to detect residual currents, which can occur as direct current (DC) and/or as alternating current (AC). Due to the increase of electronic devices in the household that can create DC-like residual currents, the detection of DC-like residual currents is becoming increasingly important to guarantee the safety of the consumers.
Residual-current circuit breakers therefore include two residual-current detection sensors, one for DC-like residual currents and one for AC-like residual currents. Such residual-current circuit breakers are technically as well as economically very complex and have high space requirements, for example because two summation current transformers are required, which is the reason why such residual-current circuit breakers are not wide-spread.
A further development of such residual-current circuit breakers would be to use only one summation current transformer, whereby the residual-current sensors for direct-current and alternating-current access the summation current transformer alternately. However, this requires a switch that is switching between the two residual-current sensors.
The disadvantage of this is that this switch is constantly in operation and thereby causes interfering signals. In addition, the switch has to be operated with a high frequency so that the time period, in which one of the two residual-current sensors is inactive, does not exceed an acceptable extent. Due to the high frequency, only a small time window is available for the detection of AC-like residual currents, whereby the bandwidth is reduced and the detection of such AC-like residual currents is hindered. The high frequency also leads to a high energy consumption and thus to a high thermal stress of the switch and neighbouring components. Therefore, the switch only has a short lifespan or respectively, the switch can fail which also leads to the failure of the protection via the residual-current circuit breaker and this can result in serious, in the worst case scenario even fatal electrical accidents. In addition, such residual-current circuit breakers are still technically as well as economically very complex and they are not very wide-spread as a result.